Observations of electron precipitation correlated with drift echoes

During the 2013 BARREL balloon campaign, electron precipitation was found to occur over a range of time scales (ms to hours) and energies (10s of keV to MeV). On 26 January 2013, an energetic particle injection was observed by GOES, THEMIS, and the Van Allen Probes, followed by drift echoes of electrons with energies of 80 - 400 keV. Following the injection, BARREL observed X-rays produced in the atmosphere by precipitating electrons with likely energies less than 180 keV. However, the precipitation showed temporal variation with a dominant oscillation period of ~20 minutes, corresponding to the drift period of ~300 keV electrons as observed by MagEIS on the Van Allen Probes. Oscillations in energetic electron precipitation have been observed previously but not in conjunction with in situ measurements of the trapped population. This study shows the association between electron drift echoes and temporal features in energetic precipitation.  These multipoint observations suggest an intriguing correspondence between the drifting ~300 keV electrons and a lower energy electron precipitation mechanism yet to be identified.